• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.12
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• pp.1837-1842
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• 2010

Studies on alternative energy have been carried out for many decades because of the accelerated exhaustion of fuel. While the efficacy of solar cells is still low in comparison with that of nuclear power, solar cells have been highlighted as potential sources of alternative energy because they are environmentally friendly and have a source of unlimited energy, namely, the sun. In this study, the optimum efficiency of solar cells was simulated as a function of the incident angle of sunlight and the geometric shapes of patterns using MATLAB and MathCAD software. The foremost efficiency of the solar cell was found to be 1.10 when the thickness and width of the patterns were in the range 25-$50{\mu}m$ and 50-$100{\mu}m$, respectively. To achieve the 25 um thick layer, 100,000 cps silver paste and 500 um orifice tip has been successfully implemented with Micro-Dispensing Deposition Writing.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.3
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• pp.337-343
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• 2020

The third phase of NASA's 3D-Printed Habitat Challenge (part of a NASA's Centennial Challenges Program competition) required entrants to build a one-third-scale space exploration habitat (10 ㎡) using 3D-printing technology. This study addresses a proposed habitat (diameter: 3 m, height: 2 m) in accordance with the competition rules. The study focus is to find the most appropriate binder when KOHLS-1 was mixed for extruding and stacking as 3D printing feedstock using pellets, and to build a prototype structure as required by the competition. Unlike previous studies, this study was based around the binders and construction method, not around axis transfer velocity, flow rate, and heater temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.163-170
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• 2011

Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. In designed regenerative cooling thruster, heat flux at nozzle throat was estimated at 18 ~ 20 $MW/m^2$. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

• Journal of the Society of Naval Architects of Korea
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• v.36 no.3
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• pp.41-49
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• 1999

A feasibility study is performed for practical application of a Ventilating Water-Jet(VWJ) propulsor which attracts new attention as a candidate propulsor for super-high speed vessels. Super-cavitating foil sections are adopted for the rotor blades since the rotor is operating at ventilating condition. Wedge type and cavitator type foil sections are used for the design of rotor blades. Other geometric characteristics of rotors are selected from the Kaplan type ducted propeller rotors. The test section of KRISO cavitation tunnel is modified to perform open-water tests of the VWJ propulsors. The tests are performed both at fully-submerged and free-jet conditions. Ventilation occurred at the free-jet condition by sucking the air in the downstream side of the rotor, which easily develops as super-cavitation when the rotor operates at lower advance coefficients. Spoilers are attached at the trailing end of the pressure side of the blade section, in order to increase the lift force.

• Industry Promotion Research
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• v.5 no.2
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• pp.1-7
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• 2020

This study is a technology related to a lighting lamp that illuminates indoor or outdoor lighting with light. In more detail, a see-through window is created in all directions on a case constituting the exterior, and a jade stone processed in a thin panel form is attached to the see-through window. By constructing a lighting lamp, since the soft light is irradiated indoors or outdoors through the jade stone, it provides comfort and warmth to the user, enhances the indoor or outdoor interior effect, emits far-infrared rays and negative ions, and emits a subtle floral scent It is a technology for lighting lamps using jade stones that emit. The characteristics of the product of this research and development is that the viewing window is formed in all directions on the case constituting the exterior, and the lighting lamp is composed by attaching the processed jade stone in the form of a thin panel to the viewing window. It is meaningful that they studied lightings using jade stones that generate sounds such as Buddhist scriptures, the Bible, and Sijo.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.8
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• pp.684-691
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• 2015

A sudden increase in combustion pressure is observed in the ducted rocket combustion test equipped with pipe shaped and converging nozzle exhaust tubes. This study aims to understand the physical mechanism of abrupt change in combustion pressure using thermal choking in the exhaust tube. Results confirmed that the thermal choking of the flow inside the exhaust tube was responsible for the sudden increase in combustion pressure. Also, high pressure exponent of solid propellants is critical sensitive to the occurrence of thermal choking exhaust pipe. Additionally, numerical simulation showed that the sudden increase in combustion pressure was less possible in diverging pipe because thermal choking is more reluctant to occur.

• Fire Science and Engineering
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• v.17 no.4
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• pp.28-35
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• 2003

To analyze the transfer characteristics of $CO_2$ extinguishant when extinguishant is injected into a closed space similar to a marine engine room, a numerical simulation was performed. Flow and Concentration fields are calculated according with the variation of the fire plume,s location. The results show that tile variation of fire plumes, location greatly effected on the flow patterns and the characteristics of $CO_2$ extinguishant transfer. In case of the fire plume located at left region of the 2nd floor center in the engine room consisted of first and second floor, The effects similar to the air curtain is found and cut off the mass transfer. In the characteristics with hight, the iso-concentration line below the extinguishable limit is formed in the left region of the 1st and 2nd floor center after the $CO_2$ extinguishant is completely injected. therefore I think that the results of this study are considered to arrange the $CO_2$ injection nozzles for the $CO_2$ fire fighting equipments.

• Fire Science and Engineering
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• v.32 no.1
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• pp.76-80
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• 2018

The present study investigates the hydrodynamic force acting on the vertical wall of a portable water storage tank which has reentrant bottom topology. To numerically simulate the lapping waves in the tank, functional iterative method for the linearized Peregrine's model which numerically simulates the propagating waves over the slowly-sloped bottom topology is introduced. The numerical experiment condition is controlled to adjust the position and the height of the water supplying nozzle. Finally, it is observed that the maximum wave height at the vertical wall and the ratio of hydrodynamic force to hydrostatic one are amplified accordingly. Therefore it must be give attention to this bad effect of amplified hydrodynamic force by the supply method of fire water in order to have the structural stability of the portable water storage tank when it was used on the reentrant bottom topography.

• Fire Science and Engineering
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• v.33 no.5
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• pp.61-65
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• 2019

In the present study, the hydrodynamic force affected by a lapping wave induced by supplied falling water acting on the vertical wall of a portable water storage tank was analyzed using a nonlinear Peregrine model. The lapping wave's maximum run-up amplitudes and the hydrodynamic forces in the wall of the tank measured by linear and nonlinear Peregrine's models were compared numerically. As a result, it was concluded that the linear model may underestimate the effects on the vertical wall; therefore, it is more appropriate to use a nonlinear Peregrine model. Furthermore, this result can contribute to the stable structural designs of portable water storage tanks.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.11-18
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• 1998

This study describes sea trial tests for a waterjet propulsion system attached in the hybrid super high speed cargo ship named "Narae". A measuring technique of jet velocity, gross thrust and impeller torque for the waterjet system is explained. From the measured data in sea trial test, performance of the waterjet propulsion system is analyzed and compared with model test results of a similar waterjet system which was carried out in 1996. The erective horse power estimated from sea trial tests shows a good agreement with resistance test results of the model ship. The optimum rising height is estimated as 0.75 m, and the overall efficiency of the waterjet system is predicted as 0.315 at 15 knots. Useful data such as the pump performance, the jet efficiency, the losses of inlet duct and nozzle were obtained. Test results show a similar behavior to the model test results.